CVE-2021-23336

The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before
3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are
vulnerable to Web Cache Poisoning via urllib.parse.parse_qsl and
urllib.parse.parse_qs by using a vector called parameter cloaking. When the
attacker can separate query parameters using a semicolon (;), they can
cause a difference in the interpretation of the request between the proxy
(running with default configuration) and the server. This can result in
malicious requests being cached as completely safe ones, as the proxy would
usually not see the semicolon as a separator, and therefore would not
include it in a cache key of an unkeyed parameter.

Bugs

• <https://bugs.python.org/issue42967&gt;

Notes